Striplines have long been used to conduct microwave signals. The stripline comprises a metallic conductor disposed at a predetermined position within a grounded channel. This predetermined position is generally at the geometric center of the channel. With present manufacturing techniques, a stripline can provide the necessary broadband performance at low cost and reduced bulk and weight vis-a-vis other transmission mediums, such as coaxial cable and rigid waveguides.
Striplines are generically classified as dielectric spaced or air spaced. In dielectric spaced striplines, support for the metallic conductor is provided by a continuous sheet of dielectric material while in air spaced striplines the amount of dielectric material is reduced to a minimum by using spaced supports. Air spaced striplines are particularly advantageous since the signal attenuation per unit distance is less than with dielectric supported striplines. The problem with air spaced striplines, however, is that the existing support structure does not precisely maintain the predetermined position of the center conductor. This mislocation of the center conductor produces signal perturbations which increase with signal frequency. In the signal frequency used in telecommunications applications, these signal perturbations are particularly acute and troublesome.